Near-infrared light absorbing glass, element and filter

ABSTRACT

Provided is a near-infrared light absorbing glass with a near-infrared light absorbing element and a near-infrared light absorbing filter. When the length of the near-infrared light absorbing glass is 1 mm, transmissivity is more than 80% at the wavelength of 400 nm, and more than 85% at the wavelength of 500 nm. The near-infrared light absorbing glass contains P 5+ , Al 3+ , Li + , R 2+  and Cu 2+  represented by positive ions, wherein R 2+  represents Mg 2+ , Ca 2+ , Sr 2+  and Ba 2+ . Meanwhile, the near-infrared light absorbing glass contains O 2−  and F −  represented by negative ions. Water durability (D W ) of the near-infrared light absorbing glass reaches Class 1 and acid durability (D A ) reaches above Class 4. In this invention, fluorphosphate glass is used as the matrix glass and the components are designed specially, so that the melting temperature of glass can be effectively lowered and the chemical stability of the glass can be excellent.

TECHNICAL FIELD

The invention relates to a near-infrared light absorbing glass, anear-infrared light absorbing element and a near-infrared lightabsorbing filter. Particularly, the invention relates to a near-infraredlight absorbing glass for near-infrared light absorbing filters suitablefor correction of chromatic sensitivity, a near-infrared light absorbingelement formed of the glass, and a near-infrared light absorbing filterformed of the glass.

RELATED ART

In recent years, with the coverage scope of spectral sensitivity ofsemisolid photographing elements such as CCD and CMOS for digitalcameras VTR cameras ranging from the visible range to the near-infraredregion (near the wavelength of 1,100 nm), filters absorbing the lightfrom the near-infrared light region can realize a visibility similar tohuman visibility. Therefore, the demand for filters for correction ofchromatic sensitivity is growing, thus resulting in higher requirementson near-infrared light absorbing glass used to manufacture such filters.In other words, such glass is required to be supplied in a large amountbut at low cost with having a good stability.

In the prior art, the near-infrared light absorbing glass is formed byadding Cu²⁺ into phosphate or fluorphosphate. However, compared withfluorphosphate glass, phosphate glass has an inferior chemicalstability, which will cause cracks and whitish turbidness on the glasssurface in case of being exposed in a high-temperature and high-humidityenvironment for a long time.

DISCLOSURE OF THE INVENTION

A technical problem to be solved by the invention is to provide anenvironment-friendly near-infrared light absorbing glass with betterhomogeneity and excellent transmissivity in visible region, anear-infrared light absorbing element, and a near-infrared lightabsorbing filter.

To solve the technical problem, the invention provides the near-infraredlight absorbing glass. When the length of the said near-infrared lightabsorbing glass is 1 mm, the transmissivity is more than 80% at thewavelength of 400 nm, and more than 85% at the wavelength of 500 nm. Thesaid near-infrared light absorbing glass contains P⁵⁺, Al³⁺, Li⁺, R²⁺and Cu²⁺ represented by positive ions, wherein R²⁺ represents Mg²⁺,Ca²⁺, Sr²⁺ and Ba²⁺. Meanwhile, the said near-infrared light absorbingglass contains O²⁻ and F⁻ represented by negative ions. Water durability(D_(W)) of the said near-infrared light absorbing glass reaches Class 1and acid durability (D_(A)) reaches above Class 4.

Furthermore, the transmissivity of said near-infrared light absorbingglass is higher than 88% at the wavelength of 400 nm and higher than 90%at the wavelength of 500 nm in case the thickness is 1 mm.

Furthermore, the content of F⁻ is more than that of O²⁻.

Furthermore, the content of F⁻—O²⁻ is 0.1 to 20%.

Furthermore, the content of F⁻—O²⁻ is 0.1 to 10%.

Furthermore, the content of F⁻—O²⁻ is 0.1 to 3%.

Furthermore, the near-infrared light absorbing glass comprises 15 to 35%of P⁵⁺, 5 to 20% of Al³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% ofK⁺, 0.1 to 8% of Cu²⁺, 30 to 65% of R²⁺ (representing Mg²⁺, Ca²⁺, Sr²⁺and Ba²⁺), 45 to 60% of F⁻ and 40 to 55% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 20 to 30%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% ofK⁺, 1.2 to 5% of Cu²⁺, 40 to 65% of R²⁺, 48 to 57% of F⁻ and 43 to 52%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, more than 50% but less than or equal to 65% ofR²⁺, more than 50% but less than or equal to 57% of F⁻, and more than orequal to 43% but less than 50% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 54 to 65% of R²⁺, 51 to 55% of F⁻ and 45 to 49%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 54 to 60% of R²⁺, 51 to 53% of F⁻ and 47 to 49%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 15 to 35%of P⁵⁺, 5 to 20% of Al³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% ofK⁺, 0.1 to 8% of Cu²⁺, 0.1 to 10% of Mg²⁺, 1 to 20% of Ca²⁺, 15 to 35%of Sr²⁺, 10 to 30% of Ba²⁺, 45 to 60% of F⁻ and 40 to 55% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 20 to 30%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% ofK⁺, 1.2 to 5% of Cu²⁺, 2 to 8% of Mg²⁺, 5 to 15% of Ca²⁺, 21 to 30% ofSr²⁺, 15 to 30% of Ba²⁺, 48 to 57% of F⁻ and 43 to 52% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 30% of Ba²⁺, more than 50% but less than or equal to 57% ofF⁻, and more than or equal to 43% but less than 50% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 25% of Ba²⁺, 51 to 55% of F⁻ and 45 to 49% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 25% of Ba²⁺, 51 to 53% of F⁻ and 47 to 49% of O²⁻.

The near-infrared light absorbing glass, comprising 15 to 35% of P⁵⁺, 5to 20% of Al³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% of K⁺, 0.1 to8% of Cu²⁺, 30 to 65% of R²⁺ (representing Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺),45 to 60% of F⁻ and 40 to 55% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 20 to 30%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% ofK⁺, 1.2 to 5% of Cu²⁺, 40 to 65% of R²⁺, 48 to 57% of F⁻ and 43 to 52%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, more than 50% but less than or equal to 65% ofR²⁺, more than 50% but less than or equal to 57% of F⁻, and more than orequal to 43% but less than 50% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 54 to 65% of R²⁺, 51 to 55% of F⁻ and 45 to 49%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 54 to 60% of R²⁺, 51 to 53% of F⁻ and 47 to 49%of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 15 to 35%of P⁵⁺, 5 to 20% of Al³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% ofK⁺, 0.1 to 8% of Cu²⁺, 0.1 to 10% of Mg²⁺, 1 to 20% of Ca²⁺, 15 to 35%of Sr²⁺, 10 to 30% of Ba²⁺, 45 to 60% of F⁻ and 40 to 55% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 20 to 30%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% ofK⁺, 1.2 to 5% of Cu²⁺, 2 to 8% of Mg²⁺, 5 to 15% of Ca²⁺, 21 to 30% ofSr²⁺, 15 to 30% of Ba²⁺, 48 to 57% of F⁻ and 43 to 52% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 30% of Ba²⁺, more than 50% but less than or equal to 57% ofF⁻, and more than or equal to 43% but less than 50% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 25% of Ba²⁺, 51 to 55% of F⁻ and 45 to 49% of O²⁻.

Furthermore, the near-infrared light absorbing glass comprises 21 to 25%of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% ofK⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% ofSr²⁺, 21 to 25% of Ba²⁺, 51 to 53% of F⁻ and 47 to 49% of O²⁻.

The near-infrared light absorbing element is formed of the near-infraredlight absorbing glass.

The near-infrared light absorbing filter is formed of the near-infraredlight absorbing glass.

The near-infrared light absorbing glass provided by the invention isadvantageous in that fluorphosphate glass is used as the matrix glassand the components are designed specially, so that the meltingtemperature of glass can be effectively lowered and the chemicalstability of the glass can be excellent (the water durability D_(W)reaches Class 1 and the acid durability D_(A) reaches Class 4 or above);In this invention, the content of F⁻ is appropriately increased in thefluorphosphate matrix glass, and the content of F⁻ is greater than thatof O²⁻, so that the melting temperature of the glass can be loweredeffectively and excellent chemical stability of the glass can berealized. In the invention, the content of R²⁺ is increased in thefluorphosphate matrix glass to increase the alkaline content of moltenglass to prevent reducing Cu²⁺ to Cu⁺, thus realizing excellentnear-infrared light absorption property of the glass. The transmissivityof the glass provided by the invention is higher than 80% at thewavelength of 400 nm and higher than 85% at the wavelength of 500 nm incase the thickness is 1 mm. And the range of the wavelengthcorresponding to 50% transmissivity (i.e. the wavelength correspondingto λ₅₀) in the spectral transmissivity within the wavelength range of500 nm to 700 nm is 615±10 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a curve graph of the spectral transmissivity of thenear-infrared light absorbing glass in Example 1 of the invention.

SPECIFIC EMBODIMENTS

The near-infrared light absorbing glass provided by the invention isobtained through using fluorphosphate glass as the matrix glass andadding Cu²⁺ capable of absorbing the near-infrared light.

The content of positive ions hereinafter is represented by the weightpercentage of said positive ions in the total positive ions, and thecontent of negative ions hereinafter is represented by the weightpercentage of said negative ions in the total negative ions.

As an elementary component of fluorphosphate glass, P⁵⁺ is an essentialcomponent for realizing absorption in the infrared region of Cu²⁺. Whenthe content of P⁵⁺ is less than 15%, the chromatic correction is liableto be poor and the color is liable to become green; however, when thecontent is more than 35%, both the weather resistance and thedevitrification resistance of the glass are liable to be degraded;therefore, the content of P⁵⁺ is 15 to 35%, preferably 20 to 30%, morepreferably 21 to 25%.

Al³⁺ is a component for improving the vitrification resistance, weatherresistance, thermal shock resistance, mechanical strength and chemicaldurability of fluorphosphate glass. When the content of Al³⁺ is lessthan 5%, the preceding effects are unavailable; however, if the contentexceeds 20%, the near-infrared light absorption property will beweakened. Therefore, the content of Al³⁺ is 5 to 20%, more preferably 10to 15%.

Li⁺, Na⁺ and K⁺ are components for improving the melting behavior, glassforming property and transmissivity of the glass in the visible lightregion. With respect to Na⁺ and K⁺, a little amount of Li⁺ can realize abetter chemical stability of the glass. However, when the content of Li⁺exceeds 30%, the durability and workability of the glass are liable tobe degraded. Therefore, the content of Li⁺ is 1 to 30%, preferably 1 to15%, more preferably 1 to 10%, further preferably 2 to 5%.

In the invention, a little amount of Na⁺ and Li⁺ can also preferably beadded to melt together, thus effectively improving the weatherresistance of the glass. The content of Na⁺ is 0 to 10%, preferably 0 to5%, more preferably 0.5 to 3%. The content of K⁺ is 0 to 3%, and thedurability of the glass is liable to be degraded in case the content ofK⁺ is more than 3%.

R²⁺ is a component capable of effectively improving the glass formingproperty, devitrification resistance and workability of the glass, andR²⁺ here represents Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺. The near-infrared lightabsorbing filter is expected to have a high transmissivity in thevisible region. To improve the transmissivity in the visible region,copper ions are required to be introduced in the form of Cu²⁺ ratherthan Cu⁺. In case molten glass is in a reduced status, Cu²⁺ is liable tobe reduced to Cu⁺, which will result in transmissivity reduction of theglass near the wavelength of 400 nm. In the invention, the total contentof Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ is increased appropriately to increase thealkaline content of molten glass to prevent reducing Cu²⁺ to Cu⁺, thusrealizing excellent near-infrared light absorption property of theglass. However, when the total content of Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ isless than 30%, the devitrification resistance is liable to be poor; andwhen the total content exceeds 65%, the devitrification resistance isalso liable to be poor. Therefore, the total content of Mg²⁺, Ca²⁺, Sr²⁺and Ba²⁺ is 30 to 65%, preferably 40 to 65%, more preferably more than50% but less than or equal to 65%, further preferably 54 to 65%, mostpreferably 54 to 60%.

Among, Mg²⁺ and Ca²⁺ can improve the devitrification resistance,chemical stability and workability of the glass. The content of Mg²⁺ ispreferably 0.1 to 10%, more preferably 2 to 8%, further preferably 3 to7%. The content of Ca²⁺ is preferably 1 to 20%, more preferably 5 to15%, further preferably 7 to 11%.

With respect to Mg²⁺ and Ca²⁺, the components of the glass provided bythe invention are mainly added with a large amount of Sr²⁺ and Ba²⁺. Inaddition to effectively increasing the content of R²⁺ and improving thetransmissivity, Sr²⁺ and Ba²⁺ can also improve the glass formingproperty, devitrification resistance and melting behavior of the glass.Therefore, the content of Sr²⁺ is preferably 15 to 35%, more preferably21 to 30%, further preferably 23 to 28%. For the same reason, thecontent of Ba²⁺ is preferably 10 to 30%, more preferably 15 to 30%,further preferably 21 to 30%, most preferably 21 to 25%.

Copper in the glass is a key indicator of the near-infrared lightabsorption property, which exists in the form of Cu²⁺ in the glass. Whenthe content of Cu²⁺ is less than 0.1%, the near-infrared lightabsorption property is liable to be poor; however, when the contentexceeds 8%, the devitrification resistance of the glass is liable to beweakened. Thus, the content of Cu²⁺ is 0.1 to −8%, preferably 1.2 to−5%, more preferably 1.2 to −3%.

The glass provided by the invention contains negative ions componentsO²⁻ and F−. In the near-infrared light absorbing glass, when the meltingtemperature rises, Cu²⁺ is liable to be reduced to Cu⁺ and the color ofthe glass is liable to change from blue to green, which damages thecharacteristics necessary for applying the correction of chromaticsensitivity to semiconductor imaging elements.

F⁻ is an essential anionic component for lowering the meltingtemperature and improving the chemical stability of the glass. In theinvention, when the content of F⁻ is less than or equal to 45%, thechemical stability is liable to be poor; however, when the content of F⁻exceeds 60%, the reduction of Cu²⁺ is liable to be unrestrained, thecontent of Cu+ in the glass is liable to be increased, the lightabsorption at a short wavelength is liable to be increased and theinfrared light absorption is liable to be reduced due to reduction ofO²⁻ content. Therefore, the content of F− is 45 to 60%, preferably 48 to57%, more preferably more than 50% but less than or equal to 57%,further preferably 51 to 55%, most preferably 51 to 53%.

O²⁻ is an essential anionic component in the glass provided by theinvention. When the content of O²⁻ is too little, the absorption in theshort wavelength region, particularly near the wavelength of 400 nm, isliable to be higher till the color becomes green due to the fact thatCu²⁺ is reduced to Cu⁺; however, when the content of O²⁻ is excessive,the viscosity of the glass is liable to be higher, thus resulting in ahigher melting temperature and transmissivity reduction. Therefore, thecontent of O²⁻ in the invention is 40 to 55%, preferably 43 to 52%, morepreferably more than or equal to 43% but less than 50%, furtherpreferably 45 to 49%, more preferably 47 to 49%.

In this invention, the content of F⁻ is appropriately increased, and thecontent of F⁻ is greater than that of O²⁻, so that the meltingtemperature of the glass can be lowered effectively; besides, anappropriate increase of F⁻ can also realize excellent chemical stabilityof the glass. Therefore, the content of F⁻ is preferably 0.1 to 20%,further preferably 0.1 to 10%, most preferably 0.1 to 3%.

Based on specific component design, the glass provided by the inventionhas the following features in chemical stability: the water durabilityD_(W) is available to Class 1; and the acid durability D_(A) can reachClass 4, preferably Class 3 and more preferably Class 2.

The water durability D_(W) (powdered method) is calculated as per thetesting method specified in GB/T17129 according to the followingFormula:D _(W)=(B−C)/(B−A)*100

Wherein D_(W) represents the leaching percentage of the glass (%);

-   -   B represents the mass of the filter and the sample (g);    -   C represents the mass of the filter and the eroded sample (g);        and    -   A represents the mass of the filter (g).

The water durability D_(W) of the optical glass is classified as sixcategories as per the leaching percentage calculated out.

Category 1 2 3 4 5 6 Leaching <0.04 0.04-0.10 0.10-0.25 0.25-0.600.60-1.10 >1.10 Percentage (Dw)

The acid durability D_(A) (powdered method) is calculated as per thetesting method specified in GB/T17129 according to the followingFormula:D _(A)=(B−C)/(B−A)*100

Wherein D_(A) represents the leaching percentage of the glass (%);

-   -   B represents the mass of the filter and the sample (g);    -   C represents the mass of the filter and the eroded sample (g);        and    -   A represents the mass of the filter (g).

The acid durability D_(A) of the optical glass is classified as sixcategories as per the leaching percentage calculated out.

Category 1 2 3 4 5 6 Leaching <0.20 0.20-0.35 0.35-0.65 0.65-1.201.20-2.20 >2.20 Percentage (D_(A))

The optimal transmissivity properties of the glass provided by theinvention are as follows:

When the glass is 1 mm thick, the spectral transmissivity within thewavelength range of 400 nm to 1,200 nm has the following properties.

The spectral transmissivity at the wavelength of 400 nm is higher thanor equal to 80%, preferably higher than or equal to 85%, more preferablyhigher than or equal to 88%.

The spectral transmissivity at the wavelength of 500 nm is higher thanor equal to 85%, preferably higher than or equal to 88%, more preferablyhigher than or equal to 90%.

The spectral transmissivity at the wavelength of 600 nm is higher thanor equal to 58%, preferably higher than or equal to 61%, more preferablyhigher than or equal to 64%.

The spectral transmissivity at the wavelength of 700 nm is lower than orequal to 12%, preferably lower than or equal to 10%, more preferablylower than or equal to 9%.

The spectral transmissivity at the wavelength of 800 nm is lower than orequal to 5%, preferably lower than or equal to 3%, more preferably lowerthan or equal to 2.5%, further more preferably lower than or equal to2%.

The spectral transmissivity at the wavelength of 900 nm is lower than orequal to 5%, preferably lower than or equal to 3%, more preferably lowerthan or equal to 2.5%.

The spectral transmissivity at the wavelength of 1,000 nm is lower thanor equal to 7%, preferably lower than or equal to 6%, more preferablylower than or equal to 5%.

The spectral transmissivity at the wavelength of 1,100 nm is lower thanor equal to 15%, preferably lower than or equal to 13%, more preferablylower than or equal to 11%.

The spectral transmissivity at the wavelength of 1,200 nm is lower thanor equal to 24%, preferably lower than or equal to 22%, more preferablylower than or equal to 21%.

It is thus clear that the absorption within the 700-1,200 wavelengthrange of near-infrared region is strong, and that within the 400-600wavelength range of visible region is weak.

In the spectral transmissivity within the wavelength range of 500 nm to700 nm, the range of the wavelength corresponding to 50% transmissivity(i.e. the wavelength corresponding to λ₅₀) is 615±10 nm.

The transmissivity of the glass provided by the invention is a valuecalculated with a spectrophotometer as per the preceding method. Theglass sample is assumed to have two parallel planes polished optically,the light falls perpendicularly from one parallel plane and emerges fromthe other parallel plane, then the transmissivity will be obtained viadividing the intensity of emergent light by the intensity of incidentlight. The transmissivity here is also called external transmissivity.

The preceding property of the glass can excellently realize chromaticcorrection of semiconductor imaging elements such as CCD or CMOS.

The near-infrared light absorbing element provided by the invention isformed of the near-infrared light absorbing glass, applicable to laminarglass elements or lenses in near-infrared light absorbing filters,suitable for chromatic correction of solid photographing elements,having good transmissivity and chemical stability.

The near-infrared light absorbing filter provided by the invention isformed of the near-infrared light absorbing glass, thus also having goodtransmissivity and chemical stability.

EXAMPLES

The invention will be described in more detail by the followingreference examples. However, the invention is not limited to saidexamples.

Fluoride, metaphosphate, oxide, nitrate and carbonate are used as rawmaterials of the glass provided by the invention. The optical glassprovided by the invention is obtained through the following steps:weighing said raw materials according to the proportions as shown inTables 1 to 3 and placing into a platinum crucible sealed with a coverafter mixing fully, melting at 700 to 900 DEG C, settling and protectingwith oxygen simultaneously with conducting homogenization, and thenenabling the molten glass to flow out from a temperature-controlled pipeat a constant speed to form the optical glass.

Examples 1 to 20 Examples of Manufacturing the Near-Infrared LightAbsorbing Glass

TABLE 1 Examples 1 2 3 4 5 6 7 8 9 10 Positive P⁵⁺ 27.5 24.2 19.6 21.722.2 23.1 21.0 25.0 18.7 25.4 Ions % Al³⁺ 13.4 10 15.3 11.8 8.7 12.712.9 10.4 15.6 11.3 Li⁺ 2.4 3.8 4.4 5.9 7.9 2.4 2.1 3.8 3.0 1.1 Na⁺ 0.61.4 0 0 0 0 0 1.0 1.5 0 K⁺ 0 0 0 0 0.5 0 0 0 2 0 R²⁺ 54.4 56.2 57.4 57.960.3 59.6 61.1 58.0 55.8 61.2 Mg²⁺ 2.8 6.8 3.6 7.2 4.4 4.6 4.8 3.9 7.13.1 Ca²⁺ 7.1 3.9 11.5 6.9 16.1 9.9 10.5 12.5 7.7 8.4 Sr²⁺ 27.6 29.1 22.718.9 16.1 24.8 25.1 22.7 23.4 27.1 Ba²⁺ 16.9 16.4 19.6 24.9 23.7 20.320.7 18.9 17.6 22.6 Cu²⁺ 1.7 4.4 3.3 2.7 0.4 2.2 2.9 1.8 3.4 1.0 Total100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Negative F⁻52.8 54.4 53.8 55.1 51.7 51.5 52.4 51.3 52.8 50.7 Ions % O²⁻ 47.2 45.646.2 44.9 48.3 48.5 47.6 48.7 47.2 49.3 Total 100.0 100.0 100.0 100.0100.0 100.0 100.0 100.0 100.0 100.0 D_(W) 1 1 1 1 1 1 1 1 1 1 D_(A) 2 33 3 3 3 3 3 2 3

TABLE 2 Examples 11 12 13 14 15 Positive P⁵⁺ 23.5 22.9 20.1 21.9 23.0Ions % Al³⁺ 11.9 12.1 13.8 12.8 13.0 Li⁺ 2.5 3.0 2.4 2.0 4.1 Na⁺ 1.0 0.70 0 2.5 K⁺ 0 0 0 0 0 R²⁺ 59 59.1 61.2 61.3 56.2 Mg²⁺ 4.9 4.3 4.6 5.3 3.3Ca²⁺ 9.1 10.2 11.1 10.9 8.5 Sr²⁺ 26.2 25.1 23.9 24.2 23.7 Ba²⁺ 18.8 19.521.6 20.9 20.7 Cu 2.1 2.2 2.5 2.0 1.2 Total 100.0 100.0 100.0 100.0100.0 Negative F⁻ 50.6 51.1 50.8 51.9 52.5 Ions % O²⁻ 49.4 48.9 49.248.1 47.5 Total 100.0 100.0 100.0 100.0 100.0 D_(W) 1 1 1 1 1 D_(A) 4 33 4 2

TABLE 3 Examples 16 17 18 19 20 Positive P⁵⁺ 23.5 22.9 20.1 21.0 23.7Ions % Al³⁺ 11.9 12.1 12.8 12.8 13.7 Li⁺ 1.8 2.3 3.4 2.9 3.7 Na⁺ 1.7 1.40 0 1.5 K⁺ 0 0 0 0 0 R²⁺ 59 59.1 61.2 61.3 56.2 Mg²⁺ 4.9 4.3 4.6 5.3 3.3Ca²⁺ 9.1 10.2 11.1 10.9 8.5 Sr²⁺ 26.2 25.1 23.9 24.2 23.7 Ba²⁺ 18.8 19.521.6 20.9 20.7 Cu²⁺ 2.1 2.2 2.5 2.0 1.2 Total 100.0 100.0 100.0 100.0100.0 Negative F⁻ 47 51.8 48.4 51.3 49.1 Ions % O²⁻ 53 48.2 51.6 48.750.9 Total 100.0 100.0 100.0 100.0 100.0 D_(W) 1 1 1 1 1 D_(A) 3 2 2 2 2

R⁺ in Table 1-3 represents the total content of Li⁺, Na⁺ and K⁺

The preceding glass is processed into plates, two planes opposite toeach other are subjected to optical polishing to prepare the samples formeasuring the transmissivity. The spectral transmissivity of each sampleis measured with the spectrometer to acquire the transmissivity oftypical wavelength of each sample with the thickness of 1 mm.

Tables 4 to 6 illustrate the transmissivity of the glass in case thethickness is 1 mm, which indicates that the glass is excellent inchromatic correction of semiconductor imaging elements.

TABLE 4 Examples 1 2 3 4 5 6 7 8 9 10 Transmis- 400 nm 83 85 82.5 81 8581.6 83.5 88.1 83.2 88.3 sivity 500 nm 88 89 87 88 88.1 88.3 88 90.9 8890.9 (%) 600 nm 63 65 63 62.4 61.4 63.6 64 63 61.7 63 700 nm 10 8 8.4 98.5 9.4 8.7 8.2 8 8.1 800 nm 1.5 2 1.4 1.6 2.3 2.1 1.7 2.1 1.2 1.8 900nm 3 3 2.5 2.2 2 3 2.3 2.5 2.3 2.1 1000 nm 5 6 5.4 4.8 4.6 4.3 5 4.2 4.44.5 1100 nm 10.5 10.5 10.3 10.7 10.8 10.4 10.5 10.3 11.5 10.5 1200 nm 2120.4 20 20.6 20.2 21 20.8 20 20 21 λ₅₀ (nm) 615 622 614 616 609 615 616616 618 624

TABLE 5 Examples 11 12 13 14 15 Transmis- 400 nm 84 88.3 82.4 80.7 83sivity 500 nm 88 90.8 88.1 85.6 88.2 (%) 600 nm 64 60.5 61.2 58.1 63.4700 nm 10.6 9.1 11.8 10 10.2 800 nm 2.1 3.5 3.1 4.1 2.1 900 nm 5 3 4 32.5 1000 nm 6.5 6.4 5 4.7 6 1100 nm 12 13 14.2 13.4 12.5 1200 nm 24 2322 23.1 21 λ₅₀ (nm) 606 618 617 614 613

TABLE 6 Examples 16 17 18 19 20 Transmis- 400 nm 82 82.3 81.6 82.8 83sivity 500 nm 88.5 88.4 88 88 88 (%) 600 nm 64.5 63.2 64 64.2 64.6 700nm 11.6 11 10 10.1 10.2 800 nm 2.2 2.4 2.3 2.3 2.1 900 nm 3.3 3 3.4 3 31000 nm 6.4 6.6 6 6.3 6 1100 nm 12.2 12.7 12 12 12.6 1200 nm 22.8 23.121 22 23 λ₅₀ (nm) 617 612 609 624 616

FIG. 1 is a spectral curve graph of Example 1, with the horizontalordinate representing the wavelength and the longitudinal coordinaterepresents the transmissivity. As illustrated in the FIGURE, thetransmissivity at the preferable wavelength of 400 nm is higher than 80%in case the glass is 1 mm thick. For the spectral transmissivity withinthe wavelength range of 500 nm to 700 nm, the range of the wavelengthcorresponding to 50% transmissivity (i.e. the wavelength correspondingto λ₅₀) is 615±10 nm. For the spectral transmissivity within thewavelength range of 400 to 1,200 nm, the transmissivity within the rangeof 800 to 1,000 nm is the lowest. Therefore, such a region is thenear-infrared region, wherein the sensitivity of semiconductor imagingelements is not very low, so the transmissivity of filters for chromaticcorrection shall be restrained, thus reaching a sufficient low level.However, the sensitivity of semiconductor imaging elements is relativelylowered at the wavelength of 1,000 to 1,200 nm, so the transmissivity ofthe glass provided by the invention is liable to be increased.

The invention claimed is:
 1. A near-infrared light absorbing glass,wherein when the near-infrared light absorbing glass is 1 mm thick, thetransmissivity is higher than 80% at the wavelength of 400 nm, higherthan 85% at the wavelength of 500 nm, and higher than 58% at thewavelength of 600 nm, wherein said near-infrared light absorbing glasscontains P⁵⁺, Al³⁺, Li⁺, R²⁺ and Cu²⁺ represented by positive ions; R²⁺represents Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺; said near-infrared light absorbingglass also contains O²⁻ and F⁻ represented by negative ions; and thewater durability (D_(W)) of the said near-infrared light absorbing glassreaches Class 1, with the acid durability (D_(A)) above Class 4, andwherein the R²⁺ weight is 54-65% based on 100% of cation weight; F⁻ andO²⁻ comprise 100% of anion weight and O²⁻ comprises at least 40% byanion weight, provided that the content of F⁻ is more than the O⁻². 2.The near-infrared light absorbing glass as recited in claim 1, whereinwhen said near-infrared light absorbing glass is 1 mm thick, thetransmissivity is higher than 88% at the wavelength of 400 nm and higherthan 90% at the wavelength of 500 nm.
 3. The near-infrared lightabsorbing glass as recited in claim 1, wherein the content of F⁻ exceedsthe content of O⁻² by 0.1 to 20%.
 4. The near-infrared light absorbingglass as recited in claim 1, wherein the content of F⁻ exceeds thecontent of O⁻² by 0.1 to 10%.
 5. The near-infrared light absorbing glassas recited in claim 1, wherein the content of F⁻ exceeds the content ofO⁻² by 0.1 to 3%.
 6. The near-infrared light absorbing glass as recitedin claim 1, comprising by cation weight: 15 to 35% of P⁵⁺, 5 to 20% ofAl³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% of K⁺, 0.1 to 8% ofCu²⁺.
 7. The near-infrared light absorbing glass as recited in claim 1,comprising by cation weight: 20 to 30% of P⁵⁺, 10 to 15% of Al³⁺, 1 to15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% of K⁺, 1.2 to 5% of Cu²⁺, and byanion weight: greater than 50 to 57% of F⁻ and 43 to less than % of O²⁻.8. The near-infrared light absorbing glass as recited in claim 1,comprising by cation weight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 1 to10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, and byanion weight: more than 50% but less than or equal to 57% of F⁻, andmore than or equal to 43% but less than 50% of O²⁻.
 9. The near-infraredlight absorbing glass as recited in claim 1, comprising by cationweight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3%of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, and by anion weight: 51 to 55%of F⁻ and 45 to 49% of O²⁻.
 10. The near-infrared light absorbing glassas recited in claim 1, comprising by cation weight: 21 to 25% of P⁵⁺, 10to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to3% of Cu²⁺, 54 to 60% of R²⁺, and by anion weight: 51 to 53% of F⁻ and47 to 49% of O²⁻.
 11. The near-infrared light absorbing glass as recitedin claim 1, comprising by cation weight: 15 to 35% of P⁵⁺, 5 to 20% ofAl³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% of K⁺, 0.1 to 8% ofCu²⁺, 0.1 to 10% of Mg²⁺, 1 to 20% of Ca²⁺, 15 to 35% of Sr²⁺, 10 to 30%of Ba²⁺.
 12. The near-infrared light absorbing glass as recited in claim1, comprising by cation weight: 20 to 30% of P⁵⁺, 10 to 15% of Al³⁺, 1to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% of K⁺, 1.2 to 5% of Cu²⁺, 2 to 8%of Mg²⁺, 5 to 15% of Ca²⁺, 21 to 30% of Sr²⁺, 15 to 30% of Ba²⁺, and byanion weight: greater than 50 to 57% of F⁻ and 43 to less than 50% ofO²⁻.
 13. The near-infrared light absorbing glass as recited in claim 1,comprising by cation weight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 1 to10% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, 3 to 7%of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% of Sr²⁺, 21 to 30% of Ba²⁺, and byanion weight: more than 50% but less than or equal to 57% of F⁻, andmore than or equal to 43% but less than 50% of O²⁻.
 14. Thenear-infrared light absorbing glass as recited in claim 1, comprising bycation weight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to11% of Ca²⁺, 23 to 28% of Sr²⁺, 21 to 25% of Ba²⁺, and by anion weight:51 to 55% of F⁻ and 45 to 49% of O²⁻.
 15. The near-infrared lightabsorbing glass as recited in claim 1, comprising by cation weight: 21to 25% of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to3% of K⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to28% of Sr²⁺, 21 to 25% of Ba²⁺, and by anion weight: 51 to 53% of F⁻ and47 to 49% of O²⁻.
 16. A near-infrared light absorbing glass, comprisingby cation weight: 15 to 35% of P⁵⁺, 5 to 20% of Al³⁺, 1 to 30% of Li⁺, 0to 10% of Na⁺, 0 to 3% of K⁺, 0.1 to 8% of Cu²⁺, 54 to 65% of R²⁺(representing Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺), and by anion weight: 45 to 60%of F⁻ and 40 to 55% of O²⁻, wherein F⁻ and O²⁻ comprise 100% of anionweight.
 17. The near-infrared light absorbing glass as recited in claim16, comprising by cation weight: 20 to 30% of P⁵⁺, 10 to 15% of Al³⁺, 1to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% of K⁺, 1.2 to 5% of Cu²⁺, and byanion weight: 48 to 57% of F⁻ and 43 to 52% of O²⁻.
 18. Thenear-infrared light absorbing glass as recited in claim 16, comprisingby cation weight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺,0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺ and by anion weight:more than 50% but less than or equal to 57% of F⁻, and more than orequal to 43% but less than 50% of O²⁻.
 19. The near-infrared lightabsorbing glass as recited in claim 16, comprising by cation weight: 21to 25% of P⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to3% of K⁺, 1.2 to 3% of Cu²⁺, and by anion weight: 51 to 55% of F⁻ and 45to 49% of O²⁻.
 20. The near-infrared light absorbing glass as recited inclaim 16, comprising by cation weight: 21 to 25% of P⁵⁺, 10 to 15% ofAl³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% ofCu²⁺, 54 to 60% of R²⁺, and by anion weight: 51 to 53% of F⁻ and 47 to49% of O²⁻.
 21. The near-infrared light absorbing glass as recited inclaim 16, comprising by cation weight: 15 to 35% of P⁵⁺, 5 to 20% ofAl³⁺, 1 to 30% of Li⁺, 0 to 10% of Na⁺, 0 to 3% of K⁺, 0.1 to 8% ofCu²⁺, 0.1 to 10% of Mg²⁺, 1 to 20% of Ca²⁺, 15 to 35% of Sr²⁺, 10 to 30%of Ba²⁺.
 22. The near-infrared light absorbing glass as recited in claim16, comprising by cation weight: 20 to 30% of P⁵⁺, 10 to 15% of Al³⁺, 1to 15% of Li⁺, 0 to 5% of Na⁺, 0 to 3% of K⁺, 1.2 to 5% of Cu²⁺, 2 to 8%of Mg²⁺, 5 to 15% of Ca²⁺, 21 to 30% of Sr²⁺, 15 to 30% of Ba²⁺, and byanion weight: 48 to 57% of and 43 to 52% of O²⁻.
 23. The near-infraredlight absorbing glass as recited in claim 16, comprising by cationweight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 1 to 10% of Li⁺, 0.5 to 3%of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% ofCa²⁺, 23 to 28% of Sr²⁺, 21 to 30% of Ba²⁺, and by anion weight: morethan 50% but less than or equal to 57% of F⁻, and more than or equal to43% but less than 50% of O²⁻.
 24. The near-infrared light absorbingglass as recited in claim 16, comprising by cation weight: 21 to 25% ofP⁵⁺, 10 to 15% of Al³⁺, 2 to 5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺,1.2 to 3% of Cu²⁺, 3 to 7% of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% of Sr²⁺,21 to 25% of Ba²⁺, and by anion weight: 51 to 55% of F⁻ and 45 to 49% ofO²⁻.
 25. The near-infrared light absorbing glass as recited in claim 16,comprising by cation weight: 21 to 25% of P⁵⁺, 10 to 15% of Al³⁺, 2 to5% of Li⁺, 0.5 to 3% of Na⁺, 0 to 3% of K⁺, 1.2 to 3% of Cu²⁺, 3 to 7%of Mg²⁺, 7 to 11% of Ca²⁺, 23 to 28% of Sr²⁺, 21 to 25% of Ba²⁺, and byanion weight: 51 to 53% of F⁻ and 47 to 49% of O².
 26. A near-infraredlight absorbing element, which is formed of the near-infrared lightabsorbing glass as recited in claim
 1. 27. A near-infrared lightabsorbing filter, which is formed of the near-infrared light absorbingglass as recited in claim 1.